Method and apparatus for monitoring the content of binary gas mixtures
First Claim
1. Apparatus for monitoring the content of a gas sample consisting essentially of two known gases, said apparatus comprising:
- means for providing a sample chamber for receiving the gas sample;
a resonant transmitter in said sample chamber excitable at a predetermined resonant frequency and operable when excited to transmit sound waves through the gas sample in said sample chamber;
means for exciting said transmitter with an excitation signal having a plurality of successive bursts each including a preselected number of excitation pulses at said resonant frequency, the initial pulse in each burst being separated from the final pulse in the immediately preceding burst by a quiescent time period of sufficient duration to allow dissipation of any transient effect that may have existed as a result of said immediately preceding burst, thereby suppressing standing waves in the sample chamber;
a resonant receiver in said sample chamber spaced a preselected distance from said transmitter and operable to receive the sound waves transmitted thereby, said receiver being resonant at said predetermined resonant frequency;
means for generating from said receiver an electrical signal representative of the transit time between said transmitter and receiver of each sound wave transmitted through the gas sample in said sample chamber; and
means for using said electrical signal to generate an output signal indicative of the ratio of the two known gases in the gas sample.
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Accused Products
Abstract
A method and apparatus for continuously monitoring the ratio of gases in a two gas mixture such as a therapeutic oxygen/nitrogen mixture. The gas mixture is passed through a sample tube within which ultrasound waves travel in successive bursts of pulses at the resonant frequency of the transmitter/receiver pair. Between bursts is a quiescent time period having a duration long enough to assure dissipation of transients so that standing waves do not form. The delay caused by the transit time of the sound through the gas sample generates electrical pulses that are translated into an analog signal which is then temperature-corrected. The resulting voltage, which is proportional to the transit time and thus to the gas composition, is compared with adjustable reference voltages to trigger high and low audio/visual alarms. A digital display provides a constant readout of the percentage of the gas component having the highest molecular weight. The sample tube is contained inside a larger cylindrical body to enhance the gas flow and provide thermal insulation which allows temperature compensation to be accurately performed.
135 Citations
16 Claims
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1. Apparatus for monitoring the content of a gas sample consisting essentially of two known gases, said apparatus comprising:
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means for providing a sample chamber for receiving the gas sample; a resonant transmitter in said sample chamber excitable at a predetermined resonant frequency and operable when excited to transmit sound waves through the gas sample in said sample chamber; means for exciting said transmitter with an excitation signal having a plurality of successive bursts each including a preselected number of excitation pulses at said resonant frequency, the initial pulse in each burst being separated from the final pulse in the immediately preceding burst by a quiescent time period of sufficient duration to allow dissipation of any transient effect that may have existed as a result of said immediately preceding burst, thereby suppressing standing waves in the sample chamber; a resonant receiver in said sample chamber spaced a preselected distance from said transmitter and operable to receive the sound waves transmitted thereby, said receiver being resonant at said predetermined resonant frequency; means for generating from said receiver an electrical signal representative of the transit time between said transmitter and receiver of each sound wave transmitted through the gas sample in said sample chamber; and means for using said electrical signal to generate an output signal indicative of the ratio of the two known gases in the gas sample. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. Apparatus for monitoring the content of a gas sample consisting essentially of two known gases, said apparatus comprising:
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a cylinder having a wall and closed first and second ends, said cylinder presenting a sample chamber for the gas sample between said ends; a transmitter mounted in said sample chamber adjacent one end of the cylinder and operable when excited to transmit sound waves through the sample chamber; a receiver mounted in said sample chamber adjacent the end thereof opposite said one end and operable to receive the sound waves; means for generating an electrical signal representative of the transit time between said transmitter and receiver of each sound wave transmitted through the gas sample in said sample chamber, thereby providing a signal indicative of the concentration ratio between the two known gases in the gas sample; a substantially cylindrical body having opposite inlet and outlet ends for receiving and discharging the gas sample respectively, said body having a diameter greater than said cylinder; means for mounting said cylinder within said body in a coaxial relationship therewith with an annular space presented between the cylinder and body; inlet port means in the wall of said cylinder adjacent said first end thereof for allowing ingress of the sample gas from said annular space into the sample chamber; and outlet port means in the wall of said cylinder adjacent said second end thereof for allowing egress of the sample gas from said sample chamber into said annular space. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A method of monitoring the content of a gas sample consisting essentially of two known-gases, said method comprising the steps of:
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transmitting sound waves through the gas sample in a plurality of successive bursts each including a preselected number of pulses at a preselected frequency with the initial pulse in each burst being separated from the final pulse in the immediately preceding burst by a quiescent time period of sufficient duration to allow dissipation of any transient effects that may have resulted from transmission of said immediately preceding burst, whereby standing waves in the sample gas are avoided; receiving each sound wave transmitted through the sample gas at a location spaced a preselected distance from the location at which the sound wave is transmitted; measuring the transit time of each sound wave from the time of its transmission to the time of its reception to provide a measure of the relative proportions of the two known gases in the gas sample; and providing a display indicative of the relative proportions of the two known gases in the gas sample. - View Dependent Claims (16)
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Specification